Creates RSA keys protocol version 1 and RSA or DSA keys for version 2 as specified with -t default RSA

Generates groups for use in Diffie-Hellman group exchange (DH-GEX).

Generates host keys for /etc/rc.

Users runs this to create their authentication key .
With SSH keys, if someone gains access to your computer, they also gain access to every system that uses that key.
To add an extra layer of security, you can add a passphrase to your SSH key.
You can use ssh-agent to securely save your passphrase so you don't have to reenter it.
Passphrase may be a string of arbitrary length, changed using -p.
Similar to a password can be a phrase of words, punctuation, numbers, whitespace, or any string.

For RSA1 keys a comment field to the user to help identify the key, changed using -c .

FILES

~/.ssh/identity

version 1 RSA authentication identity of the user. Must be not be readable by
by group or others. It is possible to specify a passphrase when generating the key which is
used to encrypt the private part using 3DES. Not automatically accessed by ssh-keygen
but is the default file for the private key. Read by ssh at login

~/.ssh/identity.pub

version 1 RSA public key. Add to ~/.ssh/authorized_keys

~/.ssh/id_dsa

version 2 DSA authentication identity of the user. Must be not be readable by
by group or others. It is possible to specify a passphrase when generating the key is
used to encrypt the private part of this file using 3DES. Not automatically accessed by ssh-keygen
but default is the file for the private key. Read by ssh at login
made.

~/.ssh/id_dsa.pub

version 2 DSA public key. Add to ~/.ssh/authorized_keys

~/.ssh/id_rsa

version 2 RSA authentication identity of the user. Must be not be readable by
by group or others. A passphrase when generating the key used to encrypt the private part of this file using 3DES. Not automatically accessed by ssh-keygen
default file for the private key. Read by ssh at login
made.

ssh-agent

ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash] [-P pkcs11_whitelist] [-t life] [command [arg ...]]
ssh-agent [-c | -s] -k
Holds private keys used for public key authentication (RSA, DSA, ECDSA, Ed25519),
started in the beginning of an X-session or a login session, and all other windows or programs are started as
clients to it. Through use of environment variables the agent can be located and automatically used
for authentication when logging in to other machines using ssh(1).

The agent initially does not have any private keys. Keys are added using ssh(1) (see AddKeysToAgent in ssh_config(5) for
details) or ssh-add(1). Multiple identities may be stored in ssh-agent concurrently and ssh(1) will automatically use
them if present. ssh-add(1) is also used to remove keys from ssh-agent and to query the keys that are held in one.

-a bind_address

Bind the agent to the UNIX-domain socket bind_address. The default is $TMPDIR/ssh-XXXXXXXXXX/agent.ppid>.

-D

Don't fork, Foreground mode.

-d

debug mode.

-E md5|sha256

default sha256.

-k

Kill the current agent (given by the $SSH_AGENT_PID

-P pkcs11_whitelist

Specify a pattern-list of acceptable paths for PKCS#11 shared libraries that may be added using -s to
ssh-add(1). default allow loading PKCS#11 libraries from ``/usr/lib/*,/usr/local/lib/*''. PKCS#11
libraries that do not match the whitelist will be refused. See PATTERNS in ssh_config(5) for a description of
pattern-list syntax.

-c

Generate C-shell commands on stdout. default if SHELL looks like it's a csh style of shell.

-s

Generate Bourne shell commands on stdout. default if SHELL does not look like it's a csh style of shell.

-t life

maximum lifetime of identities added to the agent. The lifetime may be specified in
seconds or in a time format specified in sshd_config(5). A lifetime specified for an identity with ssh-add(1)
overrides this value. default lifetime is forever.

If a command line is given, this is executed as a subprocess of the agent. When the command dies, so does the agent.

The agent is run in the user's local terminal. Authentication data need not be stored on
any other machine, and authentication passphrases never go over the network. The connection to the agent is
forwarded over SSH remote logins, and the user can thus use the privileges given by the identities anywhere in the netork in a secure way.

agent starts a new subcommand into which some environment variables are exported, eg ssh-agent xterm &.

agent output the needed shell commands
(either sh(1) or csh(1) syntax can be generated) which can be evaluated in the calling shell, eg eval `ssh-agent -s` for
Bourne-type shells such as sh(1) or ksh(1) and eval `ssh-agent -c` for csh(1) and derivatives.

Later ssh(1) looks at these variables and uses them to establish a connection to the agent.

The agent does notsend private key over its request channel. Instead, operations that require a private key will be
performed by the agent, and the result will be returned to the requester. This way, private keys are not exposed to
clients using the agent.

A UNIX-domain socket is created and the name of this socket is stored in $SSH_AUTH_SOCK. The
socket is made accessible only to the current user. This method is easily abused by root or another instance of the same
user.

$SSH_AGENT_PID holds the agent's process ID.

The agent exits when the command given on the command line terminates.

FILES

$TMPDIR/ssh-XXXXXXXXXX/agent.ppid>
UNIX-domain sockets used to contain the connection to the authentication agent. These sockets should only be
readable by the owner. The sockets should get automatically removed when the agent exits.